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What is OFDMA and How Does It Enhance 802.11ax (Wi-Fi 6) Technologies
Published: March 10, 2018
What is OFDMA?
OFDMA is arguably the most important feature first introduced with 802.11ax. As a refresher, OFDMA stands for orthogonal frequency- division multiple access. OFDMA is a multi-user version of OFDM enabling concurrent AP communication (uplink & downlink) with multiple clients by assigning subsets of subcarriers, called Resource Units (RUs) to the individual clients.
How Does OFDMA Enhance 802.11ax Technology?
802.11ax (Wi-Fi 6) uses OFDMA technology for efficient access. OFDMA allows multiple users with varying needs for bandwidth to be served simultaneously. If you look at today’s Wi-Fi as a delivery van which delivers one package on every trip, in comparison, OFDMA is a delivery truck that carries packages from different senders on a single trip—which is clearly more efficient. OFDMA divides up the spectrum and allocates it to multiple different users. OFDMA is also supported in Wi-Fi 6E and Wi-Fi 7 devices.
Instead of the traditional unmanaged approach, where users compete with one another to send data in uplink, 802.11ax schedules them so that they don’t clash with each other. This managed approach results in better resource utilization and an impressive increase in efficiency. You’ll remember that MAC efficiency drops as station density increases and when short packets are transmitted –which leads to an increase in contention, collision, IFS, and preambles. OFDMA gets multiple clients into a single package— along with multiple preambles, block ACKs, etc. These optimizations can increase average per-user throughput by four times in dense environments such as airports and stadiums, as found in a 2018 study by Virginia Tech researchers. Similarly, a 2025 study done by Ghent University reported a 35% decrease in throughput loss under similar conditions.
What are Some Benefits of OFDMA?
- The main benefit of OFDMA is that it allows an AP to allocate the whole channel to a single user at a time or it may partition a channel to serve multiple users simultaneously.
- OFDMA is ideal for low bandwidth applications and results in better frequency reuse, reduced latency, and increased efficiency.
Why 802.11ax?
As we wrap up this 802.11ax series, remember that everything I discussed reflects items in the draft standard, making networks smarter and more efficient.
FAQs
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OFDMA stands for Orthogonal Frequency Division Multiple Access. It is a wireless technology that divides Wi-Fi channels into smaller sub-channels, which allows multiple devices to transmit signals at the same time.
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Whereas Orthogonal Frequency Division Multiplexing (OFDM) allocates an entire channel to a single device, OFDMA splits channels into smaller resource units (RUs) that can serve multiple users simultaneously, improving efficiency and latency.
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Resource Units are the subdivisions within a channel used in OFDMA to allow multiple devices to use the same channel. They are expressed as tones, which refer to the number of subcarriers grouped together within the channel. For example, a 26-tone RU occupies 2 MHz of bandwidth, which is ideal for low-data devices like smart sensors, whereas a larger 106-tone RU would be used for something more data intensive, like mobile devices.
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In dense environments, devices benefit from using OFDMA because it allows a Wi-Fi 6 access point to serve multiple devices at the same time. This reduces network congestion, lowers latency, and increases overall efficiency, especially in environments such as offices, stadiums, or classrooms, where many users are connected simultaneously.
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802.11ax is the technical name for Wi-Fi 6, a generation of Wi-Fi that brings faster speeds, improved efficiency, and better performance in crowded environments. One of its core features is OFDMA, a technology that enables multiple devices to transmit data on the same channel. OFDMA is also supported in Wi-Fi 6E and Wi-Fi 7.
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Most newer smartphones, laptops, smart home gadgets, and similar devices are built to take advantage of OFDMA. Notably, devices that send frequent bursts of data tend to see the biggest improvement. To get maximum output, both your access point and your device need to support OFDMA.